mysql count group by having

Question

I have this table:

Movies (ID, Genre)

A movie can have multiple genres, so an ID is not specific to a genre, it is a many to many relations

Answer 1

One way would be to use a nested query:

SELECT count(*)
FROM (
   SELECT COUNT(Genre) AS count
   FROM movies
   GROUP BY ID
   HAVING (count = 4)
) AS x

The inner query gets all the movies that have exactly 4 genres, then outer query counts how many rows the inner query returned.